Cavity-resonator magnetron



i J. VERWEEL Jan. 20, 1959 fCAVITY-RESQNATOR MAGNETRON Filed June 6, 1955 NVENTQR JA'N VERWEEL wy AGENT I Unite States Patent 2,870,375 cAvrrY-aEsoNAToR MAGNETRON assignor, by mesne Jan Verweei, Eindhoven, Netherlands, I

assignments, to North American Philips Company, New York, N. Y., a corporation of Delaware This invention relates to cavity-resonator magnetrons, and in particular to cathode support constructions for such magnetrons.

In magnetrons of the rising-sun type, a cylindrical cathode in an anode block is surrounded by a plurality of cavity resonators substantially extending as radial grooves which are alternately deep and shallow and which at the two end surfaces of the anode block communicate with the end spaces of the magnetron, the oathode being supported by a construction arranged in line therewith and extending through one of the pole-pieces of the magnetron.

Such magnetrons of the rising-sun type are known not only with this axial support for the cathode, but also with radial cathode supports; that is to say, the cathode is supported by two heating-current supply wires which at the extremities of the cathode extend to the outside at right angles to the axis of the magnetron.

However, the axial cathode support affords the advantage of an improved dissipation of heat from the cathode, which is rather considerable during oscillation. A disadvantage is that this type of magnetron frequently is not particularly stable in operation, especially for high values of the magnetic field.

The chief object of the invention is to provide an improved magnetron of the foregoing type.

In accordance with the invention, in an axial support construction for the cathode of such magnetrons, at least one extremity of the cathode is surrounded by a conductive ring including a radial extension in which either the ring is connected to the cathode, or the extension is connected to the anode in a conductive manner. It has been found that magnetrons according to the invention are stabler in operation than without the ring with the radial extension, and furthermore their high-frequency output is considerably higher, since the magnetic field may be increased.

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The invention will now be described with reference to the accompanying drawing wherein:

Fig. l is a cross-sectional view at right angles to the cathode axis of a magnetron according to the invention.

Fig. 2 is a view of the magnetron of Fig. 1 along the line IIII.

In Figs. 1 and 2, the anode block 1 of the magnetron comprises alternatelyarranged deep and shallow grooves 2 and 3 as is common with magnetrons of the rising-sun type. The cathode 4 is supported by an axial support member 5. The cathode contains an inner filament 6, and the extremity of the electron-emissive portion of the cathode 4 is defined by a ring or end hat 8 provided therearound. The axial cathode lead 5 extends through a pole-piece 9, of which the vacuum-tight connection with the anode block is not shown. The extremity of the cathode is surrounded by a conductive ring 10 having an inner diameter equal to that of the anode block. The ring 10 is secured to the anode block by means of a conductive pin or radial extension 11. As will be noted, the ring 10 is mounted within one of the end spaces of the magnetron. A tentative explanation of the function of ring 10 may be that as its capacitance against the cathode is rather great, currents will flow through extension 11. These currents will disturb the symmetry of the end space, and as a consequence ensure stability in operation.

While we have described our invention in connection with specific embodiments and applications, other modifi cations thereof will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

l. A cavity resonator magnetron comprising a cylindrical cathode electrode; a rising-sun anode electrode having an end space; an axial support for said cathode; a conductive annular ring surrounding said cathode electrode in said end space and having an inner diameter substantially equal to the inner diameter of said anode electrode; and a radial extension extending from said ring and conductively attached to said anode electrode.

2. A cavity resonator magnetron as set forth in claim 1 in which said cathode electrode has a radially extending end hat in the same plane as said ring.

References {Iited in the tile of this patent UNITED STATES PATENTS 2,408,234 Spencer Sept. 24, 1946 2,465,211 Donal et al Mar. 22, 1949 2,468,243 Spencer Apr. 26, 1949 2,480,999 Brown et al. Sept. 6, 1949 

